Muniscins

The muniscin protein family was initially defined in 2009^[4] as proteins having 2 homologous domains that are involved in clathrin mediated endocytosis (CME) and have been reviewed.^[5] In addition to FCHO1, FCHO2 and Syp1,^[6][7] SGIP1 is also included in the family because it contains the μ (mu) homology domain and is involved in CME, even though it does not contain the F-BAR domain^[1][8]

Structure of Muniscin proteins^[1] and a dimer^[2] of FCHO proteins

Ribbon representation of BAR domains from two monomers of endophilin-A1.^[3]

The μ homology domain of muniscins evolved from TCUP

Muniscins are known as alternate cargo adaptors. That is, they participate in selecting which cargo molecules are internalized via CME.^[5] Additionally, the structure of the dimer, with its concave face oriented toward the plasma membrane, is thought to help curve the membrane as the clathrin coated pit forms.^[5] The muniscins are early arriving proteins involved in CME.^[5] FCHO proteins are required for CME,^[9] but do not appear to be required to initiate CME.^[10]

The μ homology domain of muniscins has been reported to have evolved from part of an ancient cargo adaptor protein complex named TSET.^[11]

See also

• AP2 adaptor complex
• Vesicular transport adaptor protein