Gary Zieve, PhD

Gary Zieve, PhD
Associate Professor Emeritus of Pathology
Stony Brook University Medical Center
Stony Brook, NY 11794-8691
E-mail: Gary.Zieve@stonybrook.edu

Research Interests:
Our laboratory studies the structure and function of the Smith proteins and their pathology as major autoantigens in Systemic Lupus Erythematosus (SLE). Our approaches to this problem are to investigate 1) The cytoplasmic assembly of the Sm proteins with snRNA to form the Sm core particle 2) The disassembly and degradation of the Sm proteins and 3) The genomics of the larger family of LSm proteins. Throughout this work we ask: What is unusual about the Sm proteins that makes them vulnerable to becoming autoantigens in SLE?

1. SnRNP proteins are the Systemic Lupus Erythematosus Sm autoantigens
Autoimmune antibodies in 30% of the patients with systemic lupus erythematosus (SLE) recognize the Sm proteins, subunits of the heteroheptameric ring shared by small nuclear ribonucleoprotein (snRNP) particles in the cell nucleus, as autoantigens. SLE is now recognized as a syndrome, a set of malfunctions of the immune system resulting in the antigen driven production of autoantibodies. Susceptibility to SLE maps to multiple genes in the immune system and includes defects in antigen clearance. Environmental or stochastic events may also contribute to the onset. The major autoantigens recognized in SLE are single and double stranded DNA and the Sm proteins. We hypothesize that the Sm proteins are prone to becoming autoantigens because they are extremely abundant and exist in a single complex that has three properties: powerful B cell epitopes, T cell epitopes and immunostimulatory RNA species. The major B cell epitopes are the
C-termini of the SmB, SmD1 and SmD3 proteins that have the rare post-translational modification of symmetrical dimethylarginine (sDMA). The T cell epitopes stimulating the anti-Sm antibody response reside in the highly conserved beta strands of the Sm fold. And the snRNA component of the particles has extensive double stranded regions that can stimulate antigen-presenting cells through interaction with Toll-like receptor 3. One characteristic of SLE is lymphopenia. We hypothesize that the over stimulated immune system suppresses the antibody response, leading to the apoptotic death of lymphocytes. Then, as a result of defects in normal clearance, snRNP particles released from the dying lymphocytes stimulate the anti-Sm response, maintaining the diseased state through positive feed back mechanism. The initial antibody response against the snRNP particle may begin thru different paths, but in vulnerable individuals it spreads to the abundant Sm proteins which in turn perpetuate the response. Our goal is to identify the specific features of the snRNP particle that stimulate the immune response. Blocking the immune recognition of these determinants could inhibit autoantibody production and the pathology of SLE.

2. Sm proteins assemble with snRNA in the cytoplasm to form the snRNP core particle
The Sm rings assemble with snRNA in the cytoplasm from three RNA-free precursors. The three non-Sm proteins 1) pICln, 2) PRMT5 and 3) SMN assist with the assembly. The Sm ring precursors in the cytoplasm are 1) a 6S complex of SmD1D2FEG and pICln 2) a 20S complex which includes SmB, SmD3, SmD1, PRMT5 and pICln, and 3) a 2S-7S complex that includes the SmB and SmD3 proteins with pICln. PRMT5 methylates arginines found in RG repeats in the C-termini of SmB, SmD1 and SmD3. Immunofluorescent studies indicate the RNA-free complexes are distributed uniformly throughout the cytoplasm and can rearrange in response to metabolic inhibitors. During core particle assembly, snRNA binds SmBD3 followed by the SmD1D2FEG pentamer to form the ring. Final assembly occurs in a 60S complex which includes the SMN complex and PRMT5 and then snRNP particle moves into the nucleus. pICln functions as a chaperone that interacts with RNA-free Sm protein complexes but not the assembled Sm rings. The pICln protein has limited homology to the Sm fold and we hypothesize it interacts with the exposed interfaces of the Sm proteins. The SmB, SmD1 and SmD3 RNA-free Sm proteins are in equilibrium between the different complexes in the cytoplasm, however once bound to the snRNA, they are permanently assembled.

3. Sm proteins are part of the larger family of LSm proteins that have the Sm fold
The heteroheptameric ring of Sm proteins that binds the snRNAs is highly conserved throughout eukaryotes. Ten different Sm proteins, transcribed from nine genes, build four different Sm rings. The Sm ring is also homologous to the LSm rings that degrade mRNA from the 5' end in the cytoplasm and which bind a diverse set of RNAs, including the U6 snRNA, in the nucleus. The Sm and LSm proteins are characterized by the Sm fold, built from five anti-parallel beta strands with a helix stacked on top, which forms a subunit of the rings. The interaction between the subunits is centered on an anti-parallel interaction of the fourth and fifth beta strands in neighboring subunits and includes many other contacts between the subunits. The snRNAs wrap around the inner lumen of the ring, with one nucleotide bound to each of the Sm subunits. The nucleotide base is inserted into a pocket created by the loops between _-strands 3 and 4 and _-strands 4 and 5.

Description of FASTA files
Each sequence is separated by an empty line.
The first line consists of a short unique label, species, protein, and accession number.
Following the accession number are two integers, which are the amino acid position numbers
corresponding to the first residue of the (32 aa) Sm1 and (14 aa) Sm2 motifs.
The remaining lines are the sequence strings, in upper case.

Species in FASTA files (Alphabetically)