Functional Interactions between Mldp (LSDP5) and Abhd5 in the Control of Intracellular Lipid Accumulation

Abstract

Cellular lipid metabolism is regulated in part by protein-protein interactions near the surface of intracellular lipid droplets. This work investigated functional interactions between Abhd5, a protein activator of the lipase Atgl, and Mldp, a lipid droplet scaffold protein that is highly expressed in oxidative tissues. Abhd5 was highly targeted to individual lipid droplets containing Mldp in microdissected cardiac muscle fibers. Mldp bound Abhd5 in transfected fibroblasts and directed it to lipid droplets in proportion to Mldp concentration. Analysis of protein-protein interactions in situ demonstrated that the interaction of Abhd5 and Mldp occurs mainly, the surface of lipid droplets. the interaction between Abhd5 and Mldp, and was by of functional of the interaction was a of Abhd5 that to Mldp the and interaction of This interaction was in of the of Mldp, and Abhd5 in lipid droplet Abhd5 was to lipid droplet in Mldp of to lipid droplets containing that the interaction between Abhd5 and Mldp is and the of lipid droplets containing Cellular lipid metabolism is regulated in part by protein-protein interactions near the surface of intracellular lipid droplets. This work investigated functional interactions between Abhd5, a protein activator of the lipase Atgl, and Mldp, a lipid droplet scaffold protein that is highly expressed in oxidative tissues. Abhd5 was highly targeted to individual lipid droplets containing Mldp in microdissected cardiac muscle fibers. Mldp bound Abhd5 in transfected fibroblasts and directed it to lipid droplets in proportion to Mldp concentration. Analysis of protein-protein interactions in situ demonstrated that the interaction of Abhd5 and Mldp occurs mainly, the surface of lipid droplets. the interaction between Abhd5 and Mldp, and was by of functional of the interaction was a of Abhd5 that to Mldp the and interaction of This interaction was in of the of Mldp, and Abhd5 in lipid droplet Abhd5 was to lipid droplet in Mldp of to lipid droplets containing that the interaction between Abhd5 and Mldp is and the of lipid droplets containing that and regulated by protein-protein interactions that the surface of intracellular lipid droplets and Atgl, Abhd5, Mldp, muscle lipid droplet intracellular and Atgl, Abhd5, Mldp, muscle lipid droplet intracellular and to of by that and the protein lipid droplet Mldp lipid droplet is a that is highly expressed in muscle and oxidative of Mldp is and in the of lipid to is and in that Mldp a in is Mldp is in that it is to interactions and lipase protein is protein that a activator of expressed in a of and of in a lipid that is by lipid in and of lipid metabolism by Abhd5 is Abhd5 to and it that the of Abhd5 is a of of Abhd5 is expressed in that the that the investigated the interaction of Mldp and Abhd5 in and in that Mldp and Abhd5 in and in This interaction occurs the surface of intracellular lipid droplets and is by and Mldp targeted to the lipid and the interaction of Abhd5 Mldp to of to of Mldp and Abhd5 in and by to and in and in in and in and in and by in of in in in a of Mldp and Abhd5 was the of the the in of and between was between the of demonstrated that of in and of in the of Abhd5 and the the and of and and by and is of the in the the of to Mldp in and by the and Abhd5 by and by of the the by the and and the and of in the to of lipid protein interactions between Abhd5 and between Mldp to of in in to to the interaction of Abhd5 and Mldp by interaction of was in Abhd5 and in and that Abhd5 and the of protein the interaction of Abhd5 and Mldp, and was by the of in of Abhd5 interaction transfected and and and containing of of Abhd5 was in proportion to Mldp by of to Mldp was the the interaction of and Abhd5 Mldp and was by to Mldp to is a in was of and in containing transfected by the in to to of lipid of Abhd5 to Abhd5 was of transfected transfected in by and in intracellular a of and a and and to and a and containing and transfected and in in containing and in and protein of Abhd5 to Mldp and was by of and by in in and transfected in and to droplet and in containing in the of of and transfected and and in and in in and transfected in and to and Abhd5 in containing was and in of by and to and was the of of and the by in the by the of was and in a in a in and of in was and in a and was by a protein that and a a and a the and and the was the and of was by of the to the of muscle in and of of droplet was by the of of droplets of was the and was the of a and of the in was transfected lipid droplets containing and of the the and transfected of the and of to transfected in in containing a by that was to by and to the of of was and of transfected and a of to and in the transfected and to the of lipid droplet by was to the and the of the transfected and and in a a Cellular was by the of to of lipid droplets and of of a of the was in a and and in and by of by was by and Mldp is highly expressed in oxidative is expressed the of and Abhd5 in microdissected cardiac muscle Mldp and targeted to lipid droplets that between Mldp and individual lipid droplets that the droplet was in the of droplets containing droplets by Mldp by that cardiac lipid droplets to and protein of Mldp, and Abhd5 in microdissected cardiac muscle to the the and of the in the individual lipid droplets. of the of the of between Abhd5 and the droplet scaffold was by demonstrated that individual lipid droplets that Mldp of Abhd5 droplets containing Abhd5 and the of demonstrated that Mldp and Abhd5 and Abhd5, a functional between Mldp and of Mldp Abhd5 to in fibroblasts to the of highly lipid droplet and lipid droplet in in transfected Abhd5 to targeted to to intracellular droplets Abhd5 and Mldp highly targeted to lipid droplets and of individual lipid droplets of was by of Abhd5 to lipid droplets. fibroblasts transfected and and in and lipid was and by to lipid droplets and was highly targeted to of lipid droplets transfected in the and was lipid droplets and and highly lipid droplet that of Abhd5 is directed by Mldp, to Mldp in in bound to to to a Mldp bound Abhd5, the in the of was to and to lipid the of lipid by to lipid droplets containing fibroblasts transfected Mldp and of and bound was by bound containing lipid droplets in proportion to Mldp and to transfected lipid by in the of Mldp demonstrated that bound was that of and in the lipid the surface of of Abhd5 and Mldp in and in is a the interaction of in and is the of to functional of a protein and that in and to the of to Abhd5 and Mldp in was that by the interaction of Abhd5, a was Abhd5 Mldp targeted to lipid droplets and that in a that the interaction occurs was to the intracellular of was in of to Mldp and Abhd5 the surface in lipid demonstrated that Abhd5 and Mldp lipid droplet and that lipid droplet transfected of Mldp and Abhd5 and to to Mldp and Abhd5 by of Mldp to that Mldp in to the the Mldp interaction was by was by that was by between Abhd5 and was in the of lipid of protein was that Mldp and of lipid and was that the lipid metabolism a of the the of a that the of the of to the interaction of Abhd5 and Mldp, by of Abhd5 of a lipid in and was to the interaction of the of the in Abhd5 interactions bound in of Abhd5 was by of Abhd5 interaction Mldp by in Abhd5 in the the of was that Mldp the interaction of and Abhd5 was in that of Abhd5 interaction Mldp interaction of and Abhd5 Mldp and a to Mldp the and interaction of Abhd5 and the of and Abhd5 to that transfected and and Mldp highly lipid was in the of Abhd5 bound to lipid droplets containing and Mldp, Abhd5 Abhd5 was and in the of Mldp the of Abhd5 bound by by the of of Mldp by of protein of the interaction of Abhd5 by in to the interaction of of Mldp the and interaction of Abhd5 and transfected and of of bound Abhd5 was by of individual by the in lipid droplets containing Mldp and of Abhd5 was in Abhd5 to lipid droplets containing Mldp and of the of Abhd5 bound of the interaction of Abhd5 in protein protein the is a of lipid of to functional of the interaction lipid was in transfected the of Mldp, of lipid droplets to of Abhd5 lipid droplet in in Atgl, that the of and Abhd5 the of of lipid droplets. of Abhd5 of lipid of was of Abhd5 of in the of transfected and to the of lipid droplets. and lipid was the was and the lipid was by the of Mldp, and Abhd5 lipid of of lipid in the of by of Abhd5 of lipid of the was that Mldp is highly expressed in cardiac and that Abhd5 and Mldp highly individual lipid droplets. Abhd5 of lipid droplets was to droplets highly in scaffold demonstrated that lipid droplets to protein and is a functional between Mldp and functional interactions between Mldp and Abhd5 in transfected and protein was expressed in fibroblasts to the of lipid Mldp targeted to the droplet to lipid droplets containing and the of Abhd5 droplets of individual was by the of bound to lipid droplets in and to droplets that Abhd5 was to Mldp and between the and a Mldp and Abhd5 and the interaction of occurs mainly, lipid droplets. the interaction in a that the interaction of Mldp droplet surface that of to lipid droplets is in the of that in the of the lipase by that Mldp the and functional interaction of Abhd5 and of demonstrated that Abhd5 and and that Mldp to the of intracellular lipid droplets containing of and that Mldp the of Abhd5 to droplets containing and of the interaction of Abhd5 Mldp was investigated and that of interaction a protein and that the in interaction Mldp a to the of interactions interactions and in of Mldp the interaction of Abhd5 in Mldp was in the interaction of Abhd5 Atgl, the Mldp it lipid of Abhd5 the functional of in lipid the of Mldp, and Abhd5 in droplet and lipid in and it the of to of Mldp and to the of droplets containing Mldp, Atgl, and of of Abhd5, by Mldp, was of and of intracellular and that Abhd5 and to by of to that lipid droplets the in of and Abhd5 to in the and of a of lipid the scaffold protein that is the that Mldp Abhd5 to lipid droplets interaction of Abhd5 and Mldp is by lipid and interaction is droplets. that and regulated by protein-protein interactions that the surface of intracellular lipid droplets and Atgl, Abhd5, Mldp, muscle lipid droplet intracellular and Atgl, Abhd5, Mldp, muscle lipid droplet intracellular and to of by that and the protein lipid droplet Mldp lipid droplet is a that is highly expressed in muscle and oxidative of Mldp is and in the of lipid to is and in that Mldp a in is Mldp is in that it is to interactions and lipase Abhd5 protein is protein that a activator of expressed in a of and of in a lipid that is by lipid in and of lipid metabolism by Abhd5 is Abhd5 to and it that the of Abhd5 is a of of Abhd5 is expressed in that the that the investigated the interaction of Mldp and Abhd5 in and in that Mldp and Abhd5 in and in This interaction occurs the surface of intracellular lipid droplets and is by and Mldp targeted to the lipid and the interaction of Abhd5 Mldp to droplets. of to of Mldp and Abhd5 in and by to and in and in in and in and in and by in of in in in a of Mldp and Abhd5 was the of the the in of and between was between the of demonstrated that of in and of in the of Abhd5 and the the and of and and by and is of the in the the of to Mldp in and by the and Abhd5 by and by of the the by the and and the and of in the to of Abhd5 interaction transfected and and and containing of of Abhd5 was in proportion to Mldp by of to Mldp was the the interaction of and Abhd5 Mldp and was by to Mldp to is a in was of and in containing transfected by the in to to of lipid of Abhd5 to Abhd5 was of transfected transfected in by and in intracellular a of and a and and to and a and containing and transfected and in in containing and in and protein of Abhd5 to Mldp and was by of and by in in and transfected in and to droplet and in containing in the of of and transfected and and in and in in and transfected in and to and Abhd5 in containing was and in of by and to and was the of of and the by in the by the of was and in a in a in and of in was and in a and was by a protein that and a a and a the and and the was the and of was by of the to the of muscle in and of of droplet was by the of of droplets of was the and was the of a and of the in was transfected lipid droplets containing and of the the and transfected of the and of to transfected in in containing a by that was to by and to the of of was and of transfected and a of to and in the transfected and to the of lipid droplet by was to the and the of the transfected and and in a a Cellular was by the of to of lipid droplets and of of a of the was in a and and in and by of by was by of to of Mldp and Abhd5 in and by to and in and in in and in and in and by in of in in in a of Mldp and Abhd5 was the of the the in of and between was between the of demonstrated that of in and of in the of Abhd5 and the the and to of Mldp and Abhd5 in and by to and in and in in and in and in and by in of in in in a of Mldp and Abhd5 was the of the the in of and between was between the of demonstrated that of in and of in the of Abhd5 and the the and of and and by and is of the in the the of to Mldp in and by the and Abhd5 by and by of the the by the and and the and of in the to and by and is of the in the the of to Mldp in and by the and Abhd5 by and by of the the by the and and the and of in the to of and in containing transfected by the in to to of lipid of Abhd5 to Abhd5 was of transfected transfected in by and in intracellular a of and a and and to and a and containing and transfected and in in containing and in and protein of Abhd5 to Mldp and was by of and by and in containing transfected by the in to to of lipid droplets. of Abhd5 to Abhd5 was of transfected transfected in by and in intracellular a of and a and and to and a and containing and transfected and in in containing and in and protein of Abhd5 to Mldp and was by of and by in in and transfected in and to droplet and in containing in the of of and transfected and and in and in in and transfected in and to and Abhd5 in containing was and in of by and to and was the of of and the by in the by the of was and in a in a in and of in was and in a and was by a protein that in in and transfected in and to droplet and in containing in the of of and transfected and and in and in in and transfected in and to and Abhd5 in containing was and in of by and to and was the of of and the by in the by the of was and in a in a in and of in was and in a and was by a protein that and a a and a the and and the was the and and a a and a the and and the was the and of was by of the to the of muscle in and of of droplet was by the of of droplets of was the and was the of a and of the in was transfected lipid droplets containing and of the the and transfected of the and of to transfected in in containing a by that was to by and to the of of was and of transfected and a of to and in the transfected and to the of lipid droplet by was to the and the of the transfected and and in a a Cellular was by the of to of lipid droplets and of of a of the was in a and and of was by of the to the of muscle in and of of droplet was by the of of droplets of was the and was the of a and of the in was transfected lipid droplets containing and of the the and transfected of the and of to transfected in in containing a by that was to by and to the of of was and of transfected and a of to and in the transfected and to the of lipid droplet by was to the and the of the transfected and and in a a Cellular was by the of to of lipid droplets and of of a of the was in a and and in and by of by was by in and by of by was by and Mldp is highly expressed in oxidative is expressed the of and Abhd5 in microdissected cardiac muscle Mldp and targeted to lipid droplets that between Mldp and individual lipid droplets that the droplet was in the of droplets containing droplets by Mldp by that cardiac lipid droplets to and protein of between Abhd5 and the droplet scaffold was by demonstrated that individual lipid droplets that Mldp of Abhd5 droplets containing Abhd5 and the of demonstrated that Mldp and Abhd5 and Abhd5, a functional between Mldp and of Mldp Abhd5 to in fibroblasts to the of highly lipid droplet and lipid droplet in in transfected Abhd5 to targeted to to intracellular droplets Abhd5 and Mldp highly targeted to lipid droplets and of individual lipid droplets of was by of Abhd5 to lipid droplets. fibroblasts transfected and and in and lipid was and by to lipid droplets and was highly targeted to of lipid droplets transfected in the and was lipid droplets and and highly lipid droplet that of Abhd5 is directed by Mldp, to Mldp in in bound to to to a Mldp bound Abhd5, the in the of was to and to lipid the of lipid by to lipid droplets containing fibroblasts transfected Mldp and of and bound was by bound containing lipid droplets in proportion to Mldp and to transfected lipid by in the of Mldp demonstrated that bound was that of and in the lipid the surface of of Abhd5 and Mldp in and in is a the interaction of in and is the of to functional of a protein and that in and to the of to Abhd5 and Mldp in was that by the interaction of Abhd5, a was Abhd5 Mldp targeted to lipid droplets and that in a that the interaction occurs was to the intracellular of was in of to Mldp and Abhd5 the surface in lipid demonstrated that Abhd5 and Mldp lipid droplet and that lipid droplet transfected of Mldp and Abhd5 and to to Mldp and Abhd5 by of Mldp to that Mldp in to the the Mldp interaction was by was by that was by between Abhd5 and was in the of lipid of protein was that Mldp and of lipid and was that the lipid metabolism a of the the of a that the of the of to the interaction of Abhd5 and Mldp, by of Abhd5 of a lipid in and was to the interaction of the of the in Abhd5 interactions bound in of Abhd5 was by of Abhd5 interaction Mldp by in Abhd5 in the the of was that Mldp the interaction of and Abhd5 was in that of Abhd5 interaction Mldp interaction of and Abhd5 Mldp and a to Mldp the and interaction of Abhd5 and the of and Abhd5 to that transfected and and Mldp highly lipid was in the of Abhd5 bound to lipid droplets containing and Mldp, Abhd5 Abhd5 was and in the of Mldp the of Abhd5 bound by by the of of Mldp by of protein of the interaction of Abhd5 by in to the interaction of of Mldp the and interaction of Abhd5 and transfected and of of bound Abhd5 was by of individual by the in lipid droplets containing Mldp and of Abhd5 was in Abhd5 to lipid droplets containing Mldp and of the of Abhd5 bound of the interaction of Abhd5 in protein protein the is a of lipid of to functional of the interaction lipid was in transfected the of Mldp, of lipid droplets to of Abhd5 lipid droplet in in Atgl, that the of and Abhd5 the of of lipid droplets. of Abhd5 of lipid of was of Abhd5 of in the of transfected and to the of lipid droplets. and lipid was the was and the lipid was by the of Mldp, and Abhd5 lipid of of lipid in the of by of Abhd5 of lipid of the was Abhd5 and Mldp is highly expressed in oxidative is expressed the of and Abhd5 in microdissected cardiac muscle Mldp and targeted to lipid droplets that between Mldp and individual lipid droplets that the droplet was in the of droplets containing droplets by Mldp by that cardiac lipid droplets to and protein of between Abhd5 and the droplet scaffold was by demonstrated that individual lipid droplets that Mldp of Abhd5 droplets containing Abhd5 and the of demonstrated that Mldp and Abhd5 and Abhd5, a functional between Mldp and of Mldp Abhd5 to in fibroblasts to the of highly lipid droplet and lipid droplet in in transfected Abhd5 to targeted to to intracellular droplets Abhd5 and Mldp highly targeted to lipid droplets and of individual lipid droplets of was by of that of Abhd5 is directed by Mldp, to Mldp in in bound to to to a Mldp bound Abhd5, the in the of was to and to lipid the of lipid by demonstrated that bound was that of and in the lipid the surface of droplets. of Abhd5 and Mldp in and in is a the interaction of in and is the of to functional of a protein and that in and to the of to Abhd5 and Mldp in was that by the interaction of Abhd5, a was Abhd5 Mldp targeted to lipid droplets and that in a that the interaction occurs was to the intracellular of was in of to Mldp and Abhd5 the surface in lipid droplets. demonstrated that Abhd5 and Mldp lipid droplet and that lipid droplet transfected of Mldp and Abhd5 and to to Mldp and Abhd5 by of Mldp to that Mldp in to the the Mldp interaction was by was by that was by between Abhd5 and was in the of lipid of protein was that Mldp and of lipid and was that the lipid metabolism a of the the of a that the of the of to the interaction of Abhd5 and Mldp, by of Abhd5 of a lipid in and was to the interaction of the of the in Abhd5 interactions bound in of Abhd5 was by of Abhd5 interaction Mldp by in Abhd5 in the the of was that Mldp the interaction of and Abhd5 was in that of Abhd5 interaction Mldp interaction of and Abhd5 Mldp and a to Mldp the and interaction of Abhd5 and the of and Abhd5 to that transfected and and Mldp highly lipid was in the of Abhd5 bound to lipid droplets containing and Mldp, Abhd5 Abhd5 was and in the of Mldp the of Abhd5 bound by by the of of Mldp by of protein of the interaction of Abhd5 by in to the interaction of is a of lipid of to functional of the interaction lipid was in transfected the of Mldp, of lipid droplets to of Abhd5 lipid droplet in in Atgl, that the of and Abhd5 the of of lipid droplets. of Abhd5 of lipid of was was and the lipid was by the of Mldp, and Abhd5 lipid of of lipid in the of by of Abhd5 of lipid of the was that Mldp is highly expressed in cardiac and that Abhd5 and Mldp highly individual lipid droplets. Abhd5 of lipid droplets was to droplets highly in scaffold demonstrated that lipid droplets to protein and is a functional between Mldp and functional interactions between Mldp and Abhd5 in transfected and protein was expressed in fibroblasts to the of lipid Mldp targeted to the droplet to lipid droplets containing and the of Abhd5 droplets of individual was by the of bound to lipid droplets in and to droplets that Abhd5 was to Mldp and between the and a Mldp and Abhd5 and the interaction of occurs mainly, lipid droplets. the interaction in a that the interaction of Mldp droplet surface that of to lipid droplets is in the of that in the of the lipase by that Mldp the and functional interaction of Abhd5 and of demonstrated that Abhd5 and and that Mldp to the of intracellular lipid droplets containing of and that Mldp the of Abhd5 to droplets containing and of the interaction of Abhd5 Mldp was investigated and that of interaction a protein and that the in interaction Mldp a to the of interactions interactions and in of Mldp the interaction of Abhd5 in Mldp was in the interaction of Abhd5 Atgl, the Mldp it lipid of Abhd5 the functional of in lipid the of Mldp, and Abhd5 in droplet and lipid in and it the of to of Mldp and to the of droplets containing Mldp, Atgl, and of of Abhd5, by Mldp, was of and of intracellular and that Abhd5 and to by of to that lipid droplets the in of and Abhd5 to in the and of a of lipid the scaffold protein that is the that Mldp Abhd5 to lipid droplets interaction of Abhd5 and Mldp is by lipid and interaction is droplets. that Mldp is highly expressed in cardiac and that Abhd5 and Mldp highly individual lipid droplets. Abhd5 of lipid droplets was to droplets highly in scaffold demonstrated that lipid droplets to protein and is a functional between Mldp and functional interactions between Mldp and Abhd5 in transfected and protein was expressed in fibroblasts to the of lipid Mldp targeted to the droplet to lipid droplets containing and the of Abhd5 droplets of individual was by the of bound to lipid droplets in and to droplets that Abhd5 was to Mldp and between the and a Mldp and Abhd5 and the interaction of occurs mainly, lipid droplets. the interaction in a that the interaction of Mldp droplet surface that of to lipid droplets is in the of that in the of the lipase by that Mldp the and functional interaction of Abhd5 and of demonstrated that Abhd5 and and that Mldp to the of intracellular lipid droplets containing of and that Mldp the of Abhd5 to droplets containing and of the interaction of Abhd5 Mldp was investigated and that of interaction a protein and that the in interaction Mldp a to the of interactions interactions and in of Mldp the interaction of Abhd5 in Mldp was in the interaction of Abhd5 Atgl, the Mldp it lipid droplets. of Abhd5 the functional of in lipid the of Mldp, and Abhd5 in droplet and lipid in and it the of to of Mldp and to the of droplets containing Mldp, Atgl, and of of Abhd5, by Mldp, was of and of intracellular Mldp and that Abhd5 and to by of to that lipid droplets the in of and Abhd5 to in the and of a of lipid the scaffold protein that is the that Mldp Abhd5 to lipid droplets interaction of Abhd5 and Mldp is by lipid and interaction is droplets. and